Effects of common Sarawak soil types on in-ground natural durability and leachability of CCA treated hardwoods

Chong, Peter Kian Fui (2015) Effects of common Sarawak soil types on in-ground natural durability and leachability of CCA treated hardwoods. Masters thesis, Universiti Malaysia Sarawak, (UNIMAS).

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Abstract

Wood and soils are important natural resources of the land, the former widely used as structural supports in contact with the latter. Many low durability wood species exposed to soil contact has reported high incidence of decay failures in poorly treated and untreated materials depending on soil types, properties and soil microbial virulence. The main objective of this study is to determine the relationship between key Sarawak soil types i.e. red-yellow podzolic, grey-white podzolic, gley, podzols and peat soil with their specific soil characteristics on natural wood durability and CCA leaching resistance from treated wood substrates held in ground contact. The decay test in this study is according to ASTM2017 decay test methodology. In this study, soils used in laboratory decay testing were maintained at 130% of their Water Holding Capacities (WHC). For 130% of soil water holding capacity (WHC), the one-way ANOVA gave significant differences (P<0.05) for overall mean percentage mass loss of decay types in different wood species per soil types. Overall mean percentage mass losses of rubberwood and kelempayan woods were higher than engkabang wood and A. mangium heart wood. For 70% soil moisture content (MC), significantly differences (P<0.05) in wood decay mass losses attributed to different soil types, decay fungi, and interaction between different soil and decay types. Among soil types, Peat-brown rot (G. trabeum) combination yielded the highest mean percentage mass, 34.0% while podzols-soft rot (C. globosum) combination yielded the lowest mean percentage mass loss, 5.7%. Soil macronutrient (N, P, K, Ca and Mg), pH, CEC, microbial count and organic matter were significant (P<0.05) positive correlated with many decay types practically for unsterile soil-burial test. The leaching test in this study is according to the AWPA E20-04 methodology. Statistically significant (P<0.05) variations were detected between wood species and leaching of CCA and its component heavy metals. Engkabang wood yielded highest overall mean CCA losses, 620 ppm (44.0 %) while A. mangium heartwood had the least mean CCA metal losses, 324 ppm (26.0%). It is also shown that arsenic had the highest mean percentage loss, 757 ppm (53.0%) than chromium, 370 ppm (26.0%) and copper, 295 ppm (21.0%) among different soils and wood species. Determination of soil physical and chemical properties mediated by soil types were also made to explore which among these attributes were responsible for the observed CCA leaching loss from wood. Key words: decay resistance, soil types, soil properties, soft rot, white rot, brown rot, CCA Preservative, soil type, treated wood, soil properties,

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